Floating point notation is widely used in digital data processing devices to represent a much larger range of numbers than can be represented in regular binary notation. Various types of floating point notations are used. Typically, a floating point number has a sign bit (s), followed by an exponent field (e) and a mantissa or significand field (fff). Usually, the sign bit, exponent, and mantissa are applied to a formula such as: EQU Value=(-1).sup.s .times.(1.fff.sub.2).times.2.sup.e.
Digital data processing devices use floating point units (FPU) to perform operations, such as addition and subtraction, on floating point numbers. In order to add or subtract floating point numbers, the decimal points must be aligned. The process is equivalent to addition or subtraction of base ten numbers in scientific notation. In order to align the decimal points, the FPU compares the exponents of each value and, if one is bigger than the other, shifts one of the mantissas so that the decimal places line up and the exponent values are equal. Generally, the mantissa of the smaller value is right shifted and the corresponding exponent is incremented for each bit position the mantissa is shifted.
Once the decimal points are aligned, the mantissas can be added or subtracted in accordance with the sign bits. The result may need to be normalized, or left shifted, so that a one is in the most significant bit position of the mantissa. The result may also be rounded.
Most digital data processing devices, in addition to supporting floating point numbers, also support integer numbers. An integer unit is typically provided to perform integer operations, such as addition and subtraction. Such prior art digital data processing devices suffer from at least the disadvantage of increased integrated circuit (IC) area requirements. Thus, it is desirable to perform integer operations using the FPU, eliminating the need for a dedicated integer unit.